1. Field of the Invention
This invention relates to a process for the recovery of oxides of sulfur such as SO.sub.2 or SO.sub.3 from combustion waste gases.
2. Description of the Prior Art
The waste gas issuing from glass melting furnaces usually contains various oxides of sulfur which are mainly produced by the combustion of sulfur in fuel oils such as heavy oil, and dust consisting substantially of sodium sulfate (Na.sub.2 SO.sub.4) which is vaporized by the high temperature molten glass in the glass melting furnace. Heretofore, it has been difficult to remove the oxides of sulfur and the associated particles from the waste gases. Thus, the presence of these components in waste gases results in the appearance of characteristic white smoke which issues from the stacks of glass manufacturing process. Recently, because of the enactment of antipollution measures which control the pollution levels of air, it has become of utmost importance for glass manufacturers to remove the smog producing components of SO.sub.2, SO.sub.3 and Na.sub.2 SO.sub.4 from waste gases.
Various processes for the recovery of oxides of sulfur from combustion waste gases have been proposed. Most of these processes are wet processes wherein the waste gas is contacted with an absorbing solution containing an alkaline absorbent such as sodium hydroxide, sodium carbonate or sodium sulfite. The oxides of sulfur are absorbed in the absorbing solutions and are recovered in the form of sodium sulfite, sodium sulfate or sulfuric acid.
However, in the wet processes, the waste gas is cooled upon contact with the absorbing solution. Accordingly, it has been necessary to heat the waste gas again before venting the treated waste gases through the stack to the atmosphere. The absorbing solution which contains the absorbed sulfur components is usually too dilute to recover the sulfur components. A need therefore, exists for a process which effectively removes the oxides of sulfur and sodium sulfate from waste gases which avoids the difficulties of the conventional wet process.